Display screen showing a transportation boarding graphical user interface



The sole FIGURE is a front view of the display screen showing a transportation boarding graphical user interface.

The outermost dashed rectangle shows a portion of a display screen and forms no part of the claimed design. The remaining broken lines form no part of the claimed design. The space outside the border formed by the solid lines or a border formed by any solid lettering forms no part of the claimed design. 

The ornamental design for a display screen showing a transportation boarding graphical user interface, as shown and described. 